Tory MP Zac Goldsmith has urged David Cameron to "get off the fence" over a third runway at Heathrow and signal whether or not the Conservatives will go into the next election in favour of expanding the airport.
His comments on Wednesday morning follow speculation that the Cabinet reshuffle was designed in part to pave the way for a major political row over the proposed runway, which the Tories cancelled when they came to power in 2010.
On Tuesday Justine Greening lost her job as transport secretary and was sent to the relatively lower-profile Department of International Development while transport minister Theresa Villiers was moved to the Northern Ireland Office. Both women are fierce opponents of building the runway, which would see about 700 homes in west London demolished.
Goldsmith told Today on BBC Radio 4: "It's impossible to pretend this isn't a sign that you open the door to at least the possibility of a third runway."
"Have they changed their mind on Heathrow, yes or no?" he asked.
Goldsmith represents Richmond Park in south west London, a part of the city whose residents can see and hear low-flying Heathrow planes for up to 18 hours a day.
He has threatened to resign as an MP if Cameron comes out in favour of a new runway. The PM fuelled speculation that the Tories could U-turn on their Heathrow policy in June when he refused to rule one out in an answer to Goldsmith in the Commons at PMQs.
There is no suggestion that the government would U-turn and agree to a third runway before the next general election but there is speculation that the Conservative party will signal a change of policy in its next manifesto.
The Labour party - despite signing off the runway before the last election while in government - is likely to be now opposed to Heathrow expansion, as will the Lib Dems.
The government is launching a wide-ranging consultation on Heathrow which is likely to conclude sometime next year. But speaking on Wednesday morning Mayor of London Boris Johnson told Sky News: "There's lots of stuff been coming out of Whitehall to suggest that a U-turn is in progress and they want to build a third runway at Heathrow.
"All the pressure from businesses to do the third runway, that's where the Treasury seems to be focusing its hopes," he said.
"What we need to do now is to end the uncertainty over Heathrow and say 'no folks it is all right, the policy is as it has been which is to say no to a new runway both now and in the future - ie in the next two and a half years."
Business leaders and aviation experts have warned that Heathrow risks losing its "hub status", as other major airports in France, Germany and the Netherlands have the capacity to open up routes to emerging markets in China, India and Brazil.
Airports in Frankfurt and Paris have four runways each, while Schiphol in Amsterdam has six of them. Heathrow's two runways are running at near capacity.
The crisis at the UK's largest airport is temporarily being eased by allowing more simultaneous take-offs and landings on each runway, so-called "mixed mode". The government has allowed limited trials of the more intense use of the runways since last year, but this gives residents near Heathrow less respite from the roar of jet engines on take-off.
Business leaders say that it would take too long to build a new airport elsewhere, and by the time it was finished the UK aviation industry would have lost out to rivals on the near continent.
Everyone accepts that Heathrow was built in the wrong place, too close to central London and in a fog-prone area, but aviation experts believe in the medium term expanding the airport is the only way to keep up with European rivals.
Grant Shapps, the new Chairman of the Conservative party, insisted on Wednesday morning that the government's policy on Heathrow hadn't changed, but insisted that airport capacity in the south-east of England remained a pressing concern that needed to be addressed.
Prime Minister David Cameron
Deputy Prime Minister Nick Clegg
Chancellor George Osborne
Foreign Secretary William Hague
Health Secretary Jeremy Hunt
After a stressful year in the DCMS, Jeremy Hunt moves from Culture to Health, replacing Andrew Lansley.
Home Secretary Theresa May
Cabinet Office Minister Francis Maude
Chief Secretary To The Treasury Danny Alexander
Minister without Portfolio, Ken Clarke
Having stepped down from the Justice Department, Clarke is supposedly staying in Government rather than hanging up his boots. Chris Grayling will replace him as Justice Secretary.
Justice Secretary Chris Grayling
Chris Grayling, formerly in the Department of Work and Pensions, will step up to hold the job vacated by Ken Clarke.
Culture Secretary Maria Miller
Maria Miller has taken up the DCMS job after Jeremy Hunt moved to the Department of Health. Miller is one of the few new faces in the cabinet.
Defence Secretary Philip Hammond
Communities Secretary Eric Pickles
Education Secretary Michael Gove
Minister for Internation Development, Justine Greening
Greening, who has been subject to plenty of rumours since her fallout over a potential third Heathrow runway. Greening was in No 10 for over an hour on Tuesday, presumably arguing her case and battling to stay in the cabinet. She will now take over Andrew Mitchell's spot at DfID.
Transport Secretary Patrick McLoughlin
McLoughlin, who has spent the past two years handling backbench rebels as Chief Whip, moves to the DfT, taking over from under-pressure Justine Greening. Greening has yet to be moved.
Energy Secretary Ed Davey
Attorney General Dominic Grieve
Cabinet Office Minister Oliver Letwin
Warsi, one of the earlest victims of the reshuffle, has been ousted as party co-chairman and is to be replaced by Grant Shapps. Warsi instead moves to to the Foreign Office as a junior minister, while also working as faith and communities minister.
Party Co-Chairman Grant Shapps
Shapps, who was the housing minister, is bumped up to party chairman, taking over from the demoted Sayeeda Warsi.
Environment Secretary Owen Paterson
Spelman leaves her post, to be replaced by the former Northern Ireland secretary Owen Paterson.
Work And Pensions Secretary Iain Duncan Smith
Leader of the House Andrew Lansley
Despite recently setting in motion huge overhauls to the NHS, Lansley has been moved to fill Sir George Young's spot as Leader of the House. Jeremy Hunt will succeed him in the Department of Health.
Business Secretary Vince Cable
Northern Ireland Secretary Theresa Villiers
Theresa Villiers, who gave nothing away as she approached Parliament with a wide smile on her face on Tuesday, replaces Owen Paterson. Paterson has moved to Defra.
Welsh Secretary David Jones
Cheryl Gillan was one name always likely to be taken off the list, and she is replaced by David Jones, who served beneath her as a Minister for Wales.
Scottish Secretary Michael Moore
Chief Whip Andrew Mitchell
Andrew Mitchell has moved moved from the Department for International Development to the role of Chief Whip, replacing Patrick McLoughlin.
Lords Leader Lord Strathclyde